The DS212+ model has next level up processor mv6282, whereas DS214SE only have Armada 370, mv6281 processor with floating point co-processor. There is quite a large performance gap between the 6282 and 6281, which is the speed limiting component during file read and write in these machines.

Looking forward to updating my Ds213j to DSM 5.0 when I get around to it. It's essentially the same as what's been reviewed here, except it's got twice the RAM and 50% faster processor clock.

A word of warning for tweakers. Currently there is no IPKG bootstrap for Armada 370 processor. Meaning it's very hard to install packages via CLI. But most additional packages you will ever want are available through their package centre, you can even add third party repository to it, so it's all good.